Low-migration, low-odor and low-swelling sheet offset printing ink

ABSTRACT

An offset printing ink is provided which comprises a colophony-modified phenolic resin and at least one component selected from the group consisting of (A) a maleic resin, (B) a modified hydrocarbon resin, (C) a colophony resin ester and mixtures thereof. The ink further comprises a water-insoluble fatty acid ester of a multivalent alcohol which has a high steric spatial requirement, and/or ethinol.

The invention relates to a low migration, odor and swelling sheet-fedoffset printing ink which is suitable for the production of foodwrapping.

On the one hand, sheet-fed offset printing inks are known in the priorart which can be described as low as to odor and flavor. These inkscontain low odor components such as hard resins, hydrogenated mineraloil cuts, synthetic aromatic oils, alkyd resins, in particular such witha low iodine number of ≦30 g J2/100 g, and dialkyl ether such asdi-n-dodecyl ether, di-n-undecyl ether, allyl-n-octyl ether,n-hexyl-n-undecyl ether as a vehicle.

However, mass transfers of these inks to the filling material can occur,the mass transfers being assessable according to the law of diffusion.However, the German food law prohibits any mass transfer, except forcomponents which are safe with regard to health, odor and flavor andwhich are technically unavoidable. Migration of the liquid components ininks of the prior art can occur, however, which can further cause theunwanted aspect of the so-called swelling. As a result of migration, inparticular thin packing films, i.e. films under 30 μm, can be affectedby warping of the film in form of wrinkling and waves. These warps areirreversible and optically and technically non-acceptable.

Furthermore, so-called anti-swelling inks are known in the prior artwhich have a vehicle composition free of mineral oil. The seriousdisadvantage of these inks is, however, that the low-viscous vehiclecomponents can have considerable migration potentials. Therefore, it ispossible that mass transfers occur in primary packing which candisadvantageously change the odor and flavor of the filling material, inparticular of the food. Such transfers are treated, for example,according to Swiss law as impurities (“Decree on Food Additives andIngredients”—Fremd- und Inhaltsstoffe-verordnung, FIV—of Jun. 26, 1996).According to the German food law, too, it is applicable to the wrappingof food and semiluxuries that changes in odor and flavor of the fillingmaterial by the wrapping are to be avoided (§31 LMBG, section 1).

Therefore, it was an object of the invention to provide sheet-fed offsetprinting inks which are low in migration and odor as well as low inswelling, and which, therefore, do not cause any unwanted changes inodor and flavor of the wrapping and which obey the migration valuesstipulated by law, respectively.

Changes in odor and flavor of the wrapped goods caused by printing inksare tested according to DIN 10955, testing of packaging and wrappingmaterial for food. In this connection, the values must be smaller than 2in order to meet the requirements mentioned.

The object of the invention is solved by an offset printing ink whichcomprises a colophony-modified phenolic resin (A) and/or a maleic resin(B) and/or a modified hydrocarbon resin (C) and/or a colophony resinester (D),which is characterized in that it comprises one or morewater-insoluble fatty acid ester(s) of multivalent alcohols with a highsteric spatial requirement and/or of ethinols as a solvent for theresin(s).

Spatial requirement is to be understood as the three-dimensional stericmeasurement of molecules. In this connection, the steric measurements ofthe esters being employed as a solvent can amount to l_(max) of from 2.0to 7.0 nm in diameter and to a V_(mean) of from 1.0 to 21.0 nm³ involume, the indicated values referring to the maximum length of themolecules.

Furthermore, in a preferred embodiment, the offset printing inkaccording to the invention comprises multifunctional allyl esters ofmultivalent organic acids. These allyl esters are capable of oxidativedrying and during the drying process they do not produce any fragmentswhich cause sensory impairments of the wrapped food. In the oxidativedrying process, a cross-linking takes place and this results in a stableprinting ink film. This process of oxidative cross-linking of theprinted ink is caused by the salts of organic acids of cobalt and/ormanganese in concentrations of 0.05-0.2% which are contained therein.

Preference is given to allyl esters of multivalent organic acids with anacid number of 2-20 mg KOH/g (DIN 55 936), a iodine number of 50-120 gJ₂/100 g (DIN 55 936) and a viscosity of 0.5-300 mPa·s measured at 20°C. and 50 l/s as well as with a molecular weight M_(w) of 300-10000.

Furthermore, an offset printing ink is preferred which comprises apolyallyl ether, additionally. Its function basically corresponds to theone of the multifunctional allyl esters.

With the addition of multifunctional allyl esters and polyallyl ethers,respectively, it is possible to achieve the mechanical resistance whichis required in the technical application for the wrapping of food andsemiluxuries and which has so far been achieved in a majority of casesonly by coating, so that this can be dropped.

Furthermore, an offset printing ink according to the invention ispreferred which is free of mineral oil.

These inks are free of substances with a high migration potential. Theresins and special fatty acid esters with their high steric spatialrequirements contained in the vehicles of the inks and/or the fatty acidesters of ethinols are coordinated so that, also in the case of primarypacking, the mass transfer to the food is so much reduced that itdistinctly remains under the limit values stipulated by law. Moreover,in the case of direct contact between the printed ink and, for example,a polypropylene packing film there is almost no change in the dimensiondue to the prevention of a mass transfer according to the invention.This was hitherto caused by a migration to the polymer matrix which iscalled swelling of films.

Therefore, with the inks according to the invention it is the first timethat the advantageous properties low in odor, migration and swellinghave been achieved simultaneously in sheet-fed offset printing inks.Therefore, these inks are particularly suited for the production of foodwrappings under employment of, for example, cardboard and paper.

Moreover, a very substantial advantage of the offset printing inkaccording to the invention is the fact that it is based on renewable rawmaterials.

Furthermore, an offset printing ink according to the invention isparticularly preferred in which the fatty acids of the fatty acid esterscomprise a carbon chain of 6-26, in particular of 8-26, carbon atoms.The fatty acids can be saturated or unsaturated fatty acids. Thefollowing fatty acids are given as examples: octadecene acid, linolicacid, linolenic acid, elaeostearic acid, tetradecanoic acid,hexadecanoic acid, octadecanoic acid, arachic acid, dodecanoic acid,hexanoic acid, octanoic acid, decanoic acid, and docosenoic acid. Thesefatty acids can be purified by means of distillation before esterifyingthem.

An offset printing ink according to the invention is preferred in whichthe multivalent alcohols are selected from trimethylolpropane,pentaerythritol, dipentaerythritol, sorbitol and2-butyl-2-ethyl-1,3-propanediol. Furthermore, an offset printing inkaccording to the invention is preferred in which the fatty acid estersof multivalent alcohols have an acid number between 5 and 20 mg KOH/g(DIN 53402), a iodine number between 0 and 150 g J₂/100 g (DIN 55936)and a viscosity between 20 and 500 mPa·s (DIN 53229). The multivalentalcohols are polyesterified or completely esterified.

Examples for water-insoluble fatty acid esters which are employedaccording to the invention are: pentaerythritol tetracaprate,dipentaerythritol hexacaprate, pentaerythritol tetradocoseate, anddipentaerythritol hexadocoseate.

The employment of natural vegetable oils, i.e. of the correspondingtriglycerides, cannot solve the problem posed. With the employment ofthe specified offset printing ink according to the invention it wasunexpectedly possible to solve the problem for the first time.

Furthermore, an offset printing ink according to the invention ispreferred which is characterized in that that the resins have amolecular weight M_(w) of 5000-120000, an acid number of 10-40, ahydroxyl number of 20-70 and a melting range of 120-190° C. In thiscase, the measuring of the melting range is carried out according to thecapillary method.

The resins are to behave sensorially neutral and to dissolve in thementioned fatty acid esters or their mixtures without the employment ofco-solvents. Moreover, the resins are to be compatible with thementioned fatty acid esters or their mixtures. The compatibility of aresin solution and a vehicle, respectively, is defined by the hexanenumber (HEZ). The compatibility is to be in a HEZ-range between 0 and+20.

Resins with a viscosity of 10-90 Pa·s at 40% in mineral oil (CompanyHaltermann PKW-F 6/9) and with a viscosity of 20-100 Pa·s at 40% inmineral oil (Company Haltermann PKW-f 6/9 ar), respectively—eachmeasured at 50 l/s and at a temperature of 20° C.—have proved to beparticularly suited and thus preferred.

Furthermore, resins with a turbidity point of 55-150° C. at 10% inmineral oil (Company Haltermann PKW-F 6/9 af new) and with a turbiditypoint of 50-150° C. at 10% in mineral oil (Company Haltermann PKW-F6/9), respectively, have proved to be particularly suited.

An offset printing ink in which the resins (A):(B) have a quantitativeratio of 33-76:24-67 as well as an offset printing ink in which theresins (A):(B):(C) have a quantitative ratio of 22-51:23-46:16-33 haveproved to be advantageous.

Particularly advantageous and thus preferred is an offset printing inkaccording to the invention in which the resins (A) and (B) as well asthe fatty acid ester of multivalent alcohols (E) have a quantitativeratio of 17-36:13-32:45-70 as well as an offset printing ink accordingto the invention in which the resins (A), (B), (C) and (D) as well asthe fatty acid ester (E) have a quantitative ratio of(A):(B):(C):(D):(E) of 0-45:0-32:0-24:0-19:38-70.

The production of the offset printing inks is carried out in a fashionwhich is known per se.

The ratio of viscosity to tackiness of the offset printing inks shouldbe in the range of 50-120 Pa·s (50 l/s, 20° C.) to 8-14 (26° C.; rate ofmeasurement 200 rpm; 1.3 m³ ink), the tackiness being measured by meansof the Prüfbau-Inkomat (name of the measuring apparatus) of the companyDürner.

The rheological data of the offset printing inks are adjusted to therequirements of technical application and to the substrates for printingin a way which is known per se.

EXAMPLES

The offset printing inks given in the following examples were producedas follows:

(a) Production of the Vehicle

The solid components of the vehicle were dissolved under stirring andexposure to inert gas in the solvent component or solvent components,having a concentration of 50% at 180-200° C.

(b) Production of the Offset Printing Ink

The solid components were predispersed in 30%-concentration at thedissolver. After addition of the residual vehicle amount the mixture wasfinely dispersed over a three-roll mill. The viscosity/tackiness ratioof the ink is regulated over the concentration of fatty acid ester.

Example 1

An offset printing ink was produced according to the followingformulation:

Lutetia Rubin BLDN Francolor Pigments Pigment Red 57:1   18% 375 ®Ceridust 3620 ® Hoechst AG Polyethylene wax   1% Rice starch powderAlmil Leonhardt  0.5% type B GmbH Alsynol RL 62 ® Arizona Chemical KPresin 11.6% Alsynol RC 17 ® Resisa Maleic resin  8.1% Pentalyn 621 ®Hercules Colophony ester  4.2% EW-Print 1041 ® Henkel KG Pentaerythritol56.6% tetraoleate  100%

The term KP resin is understood as colophony modified phenolic resin.

Comparison Example

An offset printing ink was produced according to the followingformulation:

Sico Echtgelb D 1361 BASF AG Pigment Yellow   12% DD ® 13 Sovermol KA3174 ® Henkel KG Coconut alkyd   8% resin Magnesia 10 Magnesia GmbHMagnesium   3% carbonate Ceridust 3620 ® Hoechst AG Polyethylene wax  1% Rice starch powder Almil Leonhardt  0.5% type B GmbH Alsynol RL58 ® Arizona Chemical KP resin   11% Tergraf UZ-76 ® Resisa KP resin16.5% Mediaplast VP 2160 ® Kettlitz Chemie Synthetic   48% GmbH aromaticoil  100%

The processing of offset printing inks according to example 1 and to thecomparison example was carried out on a sheet-fed offset printingmachine of the type MAN-Roland R 700 at a printing output of 8000-12000copies/h under employment of a damping solution having 5% isopropanol.Printing was carried out at 1.5-2 g/m² on cellulose cardboard which wassuited for the production of primary packing for food.

Immediately after the printing process, the samples were tightly packedin aluminum foil and handed over to the Fraunhofer InstitutLebensmitteltechnologie und Verpackung (Fraunhofer institute for foodtechnology and wrapping), Munich, for the analysis of the migrationaccording to the Tenax method which had been developed there. The masstransfer at direct contact between the printed cardboard side andTenaxe® as a food simulator is determined by means of this method (24hours at 60° C.). Tenax® is an adsorbent which is distributed by thecompany Akzo. Tenax® is a polyphenylene oxide on the basis of2,6-diphenylphenol.

In the report prepared by the Fraunhofer Institut it was confirmed thatthe quantity of the total amount of the migrated substances of thesample of the offset printing ink according to the invention accordingto example 1 is, in contrast to the offset printing ink according to thecomparison example, not above the amount of the unprinted cardboard.Therefore, prints produced with the offset printing ink according to theinvention do not have elevated migration values in comparison to theunprinted cardboard.

Furthermore, in-house tests had the following results:

(a) Cardboard cuttings which had been printed on with the offsetprinting ink according to the invention did virtually cause no swellingin contact with a 16 μm thick polypropylene film.

(b) The sensory tests according to Robinson with regard to odor andflavor of prints with the ink according to the invention resulted in anevaluation which was clearly below 2. This means that the requirementsto low odor inks were completely met.

With the employment of the offset printing inks according to the presentinvention the mass transfer, which is considered to be technicallyunavoidable according to §31, section 1 of the food and requisite law,is very substantially reduced or eliminated in comparison to the inks ofthe prior art.

Example 2

An offset printing ink was produced according to the followingformulation:

Irgalith Blau GLG ® Ciba Geigy GmbH Pigment Blue   15% Ceridust 3620 ®15:3   1% Rice starch powder  0.5% type B XR-1769 Lawter InternationalKP resin  7.6% Jonrez RP-372 ® Westvaco KP resin   21% Priolube 1427 ®Unichema Trimethylol- 54.9% International propane trioleate  100%

Example 3

An offset printing ink was produced according to the followingformulation:

Sico Echtgelb D 1361 BASF AG Pigment Yellow 13   12% DD ® Ceridust3620 ® 1% Rice starch powder  0.5% type B Resenol 9080 ® D.R.T. KP resin14.3% Tergraf UZ-79 ® Resisa KP resin 11.5% BOE-HS 201 ® BOE-ChemieAllyl ester of multi- 11.3% valent organic acids Crodamol PTC ® CrodaGmbH Pentaerythritol 47.4% tetracaprate Co-Mn-octoate 2/6.5% in Abshagen&   2% the combination with Co KG soya  100%

Example 4

An offset printing ink was produced according to the followingformulation:

Lutetia Rubin BLDN   18% 375 ® Ceridust 3620 ®   1% Rice starch powder 0.5% Jonrez IM 832 ® Arizona Chemical KP resin 14.1% Alsynol RL 25N ®Arizona Chemical KP resin  9.9% BOE-HS 201 ® BOE-Chemie Allyl ester of 9.2% multivalent organic acids Crodamol TMP-CC ® Croda GmbHTrimethylolpropane 45.3% tricapryl/caprate Co-Mn-octoate   2% 2/6.5% inthe combination with soya  100%

Example 5

An offset printing ink was produced according to the followingformulation:

Elftex 415 ® Cabot GmbH Pigment Black 7   18% Ceridust 3620 ®   1% Ricestarch powder type B  0.5% Tergraf ND-1243 ® Resisa KP resin 13.1%Ultrarez 8226 ® Lawter KP resin 10.9% International Crodamol PTIS ®Croda GmbH Pentaerythritol 56.5% tetraisostearate  100%

The processing of the examples 2 to 5 was carried out on a sheet-fedoffset printing machine of the type MAN-Roland R 700 at a printingoutput of 8000-12000 copies/h under employment of a damping solutionhaving 5% isopropanol. In this case, printing was carried out on coatedand uncoated paper and cardboard types, the fibrous substance consistingof wood pulp, cellulose or recycling fibres. The offset printing inkswere manufactured in an uncoated state or in a coated state (inline withemulsion paint).

In all cases, it turned out that the abrasion resistance, coatingadhesion, drying and subsequent treatment met the high requirements ofthe producers of packing means. Therefore, with regard to theseessential properies the inks according to the invention were, at least,equal to the offset printing inks for the printing of packing of theprior art. Just as well did the printability and printing quality onhigh-speed sheet-fed offset printing machines, too, meet at least thequality standard of the inks of the prior art. However, the inksaccording to the invention made it possible now to make use of renewableraw materials as starting materials for offset printing ink componentsand, moreover, to provide inks which show low odor, flavor as well aslow swelling.

These advantageous surprising properties of the offset printing ink arebased on the selection and combination of the resins and fatty acidesters according to the invention.

What is claimed is:
 1. Offset printing ink composition comprising atleast one component selected from the group consisting of (A) acolophony-modified phenolic resin, (B) a maleic resin, (C) a modifiedhydrocarbon resin, (D) a colophony resin ester, and mixtures thereof,said composition further comprising at least one component selected fromthe group consisting of a water-insoluble fatty acid ester of amultivalent alcohol having a high steric spatial requirement, awater-insoluble fatty acid ester of ethinol, and a mixture thereof, saidesters having steric dimensions of the diameter l_(max) of from about2.0 to about 7.0 nm and the volume V_(mean) of from about 1.0 to about21.0 nm³.
 2. Offset printing ink composition as in claim 1 characterizedin that said composition further comprises a multifunctional allyl esterof a multivalent organic acid.
 3. Offset printing ink composition as inclaim 2 characterized in that said fatty acid of the fatty acid esterhas a carbon chain containing from about 6 to about 26 carbon atoms. 4.Offset printing ink composition as in claim 2 characterized in that saidresins A, B, C and D each has molecular weight M_(w) of from about 5000to 120,000, an acid number of from about 10 to about 40, a hydroxylnumber of from about 26 to about 70 and a melting range of from about120 to about 190° C.
 5. Offset printing ink composition as in claim 1characterized in that said composition further comprises a polyallylether.
 6. Offset printing ink composition as in claim 5 characterized inthat said fatty acid of the fatty acid ester has a carbon chaincontaining from about 6 to about 26 carbon atoms.
 7. Offset printing inkcomposition as in claim 5 characterized in that said multivalent alcoholis selected from the group consisting of trimethylolpropane,pentaerythritol, dipentaerythritol, sorbitol,2-butyl-2-ethyl-1,3-propanediol and mixtures thereof.
 8. Offset printingink composition as in claim 5 characterized in that said resins A, B, Cand D each has molecular weight M_(w) of from about 5000 to 120,000, anacid number of from about 10 to about 40, a hydroxyl number of fromabout 26 to about 70 and a melting range of from about 120 to about 190°C.
 9. Offset printing ink composition as in claim 1 characterized inthat said fatty acid of the fatty acid ester has a carbon chaincontaining from about 6 to about 26 carbon atoms.
 10. Offset printingink composition as in claim 1 characterized in that said multivalentalcohol is selected from the group consisting of trimethylolpropane,pentaerythritol, dipentaerythritol, sorbitol,2-butyl-2-ethyl-1,3-propanediol and mixtures thereof.
 11. Offsetprinting ink composition as in claim 1 characterized in that said resinsA, B, C and D each has molecular weight M_(w) of from about 5000 to120,000, an acid number of from about 10 to about 40, a hydroxyl numberof from about 26 to about 70 and a melting range of from about 120 toabout 190° C.